1. Field of the Invention
The instant invention is directed to a method of controlling corn rootworm. Most particularly, the instant invention is directed to a method for combating corn rootworm with an effective amount of N-methyl 2-(1-methylethyl)phenylcarbamate.
2. Description of the Prior Art
Corn rootworms are the larvae of several species of beetles of the genus Diabrotica. These larvae cause severe damage to the roots of corn plants, particularly in fields where one corn crop follows another in successive seasons. The adult beetles lay their eggs in the soil of a maturing crop corn. The eggs lay dormant in the soil until the following spring. Then they hatch in response to favorable soil temperatures and the larvae feed on the roots of young corn plants causing reduction in yield and/or the stalks to topple over when subjected to either wind or wet soil conditions. The fallen stalks cannot be satisfactorily harvested by mechanical harvesters causing significant losses.
One method of combating corn rootworm, known in the prior art, is to apply an insecticidally effective amount of N-methyl 3-(1-methylethyl)phenylcarbamate to the soil around which the corn is planted. This method is disclosed in U.S. Pat. No. 3,250,673, May 10, 1966 (Bagley). It is noted that this reference refers to this compound as 3-isopropylphenyl N-methylcarbamate or meta-isopropylphenyl N-methylcarbamate (herein called MIC). This compound is recited, in the patent, to be effective, against corn rootworm. The reference further teaches the application of the MIC months after planting of seeds, that is, MIC application is a task separate from planting and at a time when the eggs have hatched and the corn has already grown. One of ordinary skill in the art will realize that treating a field of corn that has attained considerable growth is a difficult and time consuming undertaking and may do physical damage to the already existing corn plants. Application rates of from 2-4 lbs/a (2.24-4.48 kg/a) are also mentioned.
The ortho-isomer of MIC is N-methyl 2-(1-methylethyl)phenylcarbamate (herein called OIC) a known foliar insecticide. This insecticide, applied directly to plants, is commercially used in the protection of rice crops. However, OIC has never been known to be effective in the control of soil insects. That is, OIC has never been suggested to be used as a soil insecticide.